Online Etymology Dictionary

dragon (n.): early 13c., from Old French dragon, from Latin draconem (nominative draco) "huge serpent, dragon," from Greek drakon (genitive drakontos) "serpent, giant seafish," apparently from drak-, strong aorist stem of derkesthai "to see clearly," from PIE *derk- "to see." Perhaps the literal sense is "the one with the (deadly) glance."

The young are dragonets (14c.). Obsolete drake "dragon" is an older borrowing of the same word. Used in the Bible to translate Hebrew tannin "a great sea-monster," and tan, a desert mammal now believed to be the jackal.
Komodo dragon (n.): 1927, named for Indonesian island of Komodo, where it lives.
dragonfly (n.): 1620s, from dragon + fly (n.).
dragoon (n.): 1620s, from French dragon "carbine, musket," because the guns the soldiers carried "breathed fire" like dragons (see dragon). Also see -oon.
Draco (n.): northern constellation representing a dragon, from Latin draco "dragon" (see dragon). Identified as such since ancient times.
drake (n.2): archaic for "dragon," from Old English draca "dragon, sea monster, huge serpent," from Proto-Germanic *drako (source also of Middle Dutch and Old Frisian drake, Dutch draak, Old High German trahho, German drache), an early borrowing from Latin draco (see dragon).
rankle (v.): c. 1300, "to fester," from Old French rancler, earlier raoncler, draoncler "to suppurate, run," from draoncle "abscess, festering sore," from Medieval Latin dracunculus, literally "little dragon," diminutive of Latin draco "serpent, dragon" (see dragon). The notion is of an ulcer caused by a snake's bite. Meaning "cause to fester" is from c. 1400. Related: Rankled; rankling.
tarragon (n.): Artemisia Dracunculus, Eastern European plant of the wormwood genus, 1530s, from Medieval Latin tragonia, from Byzantine Greek tarchon, from Arabic tarkhon, from a non-Arabic source, perhaps Greek drakon "serpent, dragon" (via drakontion "dragonwort"); see dragon. From the same source come Spanish taragona, Italian targone, French estragon (with unetymological prefix). Its aromatic leaves long have been used for flavoring (especially vinegar).
draconian (adj.): 1876 (earlier Draconic, implied from 1640s), from Draco, Greek statesman who laid down a code of laws for Athens 621 B.C.E. that mandated death as punishment for minor crimes. His name seems to mean literally "sharp-sighted" (see dragon).
snapdragon (n.): garden plant, 1570s, from snap (n.) + dragon. So called from fancied resemblance of antirrhinum flowers to a dragon's mouth. As the name of a Christmas game of plucking raisins from burning brandy and eating them alight, from 1704.
pendragon (n.): "Welsh warlord" (mainly known now in Arthurian Uther Pendragon), late 15c., title of a chief leader in war of ancient Britain or Wales, from pen "head" (see pen-) + dragon, which figured on the standard of a cohort.
oolong (n.): dark variety of Chinese tea, 1852, from Chinese wu-lung, literally "black dragon."
sea-monster (n.): 1580s, from sea + monster. Sea serpent is attested from 1640s. In Old English a sea-monster might be called sædraca "sea dragon," or sædeor.
Dracula (n.): the vampire from in Bram Stoker's novel (1897). It was a surname of Prince Vlad II of Wallachia (d.1476), and means in Romanian "son of Dracul," literally "the dragon," from the name and emblem taken by Vlad's father, also named Vlad, c. 1431 when he joined the Order of the Dragon, founded 1418 by Sigismund the Glorious of Hungary to defend the Christian religion from the Turks and crush heretics and schismatics.
wyvern (n.): c. 1600, formed (with excrescent -n) from Middle English wyver (c. 1300), from Anglo-French wivre, from Old North French form of Old French guivre "snake," from Latin vipera "viper" (see viper). In heraldry, a winged dragon with eagle's feet and a serpent's barbed tail.
shard (n.): also sherd, Old English sceard "incision, cleft, gap; potshard, a fragment, broken piece," from Proto-Germanic *skardas (source also of Middle Dutch schaerde "a fragment, a crack," Dutch schaard "a flaw, a fragment," German Scharte "a notch," Danish skaar "chink, potsherd"), a past participle from the root of Old English sceran "to cut" (see shear). Meaning "fragment of broken earthenware" developed in late Old English. Used late 14c. as "scale of a dragon." French écharde "prickle, splinter" is a Germanic loan-word.
zymurgy (n.): branch of chemistry which deals with wine-making and brewing, 1868, from Greek zymo-, comb. form of zyme "a leaven" (from PIE root *yeue-; see juice) + -ourgia "a working," from ergon "work" (see organ).

The last word in many standard English dictionaries (and this one); but Century Dictionary ends with Zyxomma ("A genus of Indian dragon-flies") and in the OED [2nd ed.] the last word is zyxt, an obsolete Kentish form of the second person singular of see (v.).
At the dictionary's letter A
Mr. Brandt is young and gay
But when at last he reaches zed
He's in his wheelchair, nearly dead

[Einar Haugen]
griffin (n.): c. 1200 (as a surname), from Old French grifon "a bird of prey," also "fabulous bird of Greek mythology" (with head and wings of an eagle, body and hind quarters of a lion, believed to inhabit Scythia and guard its gold), named for its hooked beak, from Late Latin gryphus, misspelling of grypus, variant of gryps (genitive grypos) "griffin," from Greek gryps (genitive grypos) "a griffin or dragon," literally "curved, hook-nosed" (opposed to simos).

Klein suggests a Semitic source, "through the medium of the Hittites," and cites Hebrew kerubh "a winged angel," Akkadian karibu, epithet of the bull-colossus (see cherub). The same or an identical word was used in mid-19c. Louisiana to mean "mulatto" (especially one one-quarter or two-fifths white) and in British India from 1793 to mean "newly arrived European," probably via notion of "strange hybrid animal."
spook (n.): 1801, "spectre, apparition, ghost," from Dutch spook, from Middle Dutch spooc "spook, ghost," from a common Germanic source (German Spuk "ghost, apparition," Middle Low German spok "spook," Swedish spok "scarecrow," Norwegian spjok "ghost, specter," Danish spøg "joke"), of unknown origin. According to Klein's sources, possible outside connections include Lettish spigana "dragon, witch," spiganis "will o' the wisp," Lithuanian spingu, spingeti "to shine," Old Prussian spanksti "spark."

Meaning "undercover agent" is attested from 1942. The derogatory racial sense of "black person" is attested from 1940s, perhaps from notion of dark skin being difficult to see at night. Black pilots trained at Tuskegee Institute during World War II called themselves the Spookwaffe.
leviathan (n.): late 14c., "sea monster, sea serpent," sometimes regarded as a form of Satan, from Late Latin leviathan, from Hebrew livyathan "dragon, serpent, huge sea animal," of unknown origin, perhaps from root l-w-h- "to wind, turn, twist," on the notion of a serpent's coils. If so, related to Hebrew liwyah "wreath," Arabic lawa "to bend, twist." Of powerful persons or things from c. 1600. Hobbes's use is from 1651.
An aquatic animal mentioned in the Old Testament. It is described in Job xli. apparently as a crocodile; in Isa. xxvii 1 it is called a piercing and a crooked serpent; and it is mentioned indefinitely in Ps. lxxiv. 14 as food and Ps. civ. 26. [Century Dictionary]
George: masc. personal name, from French Georges, Late Latin Georgius, from Greek Georgos "husbandman, farmer," properly an adjective, "tilling the ground," from ge "earth" (see Gaia) + ergon "work" (see organ). The name introduced in England by the Crusaders (a vision of St. George played a key role in the First Crusade), but not common until after the Hanoverian succession (18c.). St. George began to be recognized as patron of England in time of Edward III, perhaps because of his association with the Order of the Garter (see garter). His feast day is April 23. The legend of his combat with the dragon is first found in "Legenda Aurea" (13c.). The exclamation by (St.) George! is recorded from 1590s.
The cult of George reached its apogee in the later Middle Ages: by then not only England, but Venice, Genoa, Portugal, and Catalonia regarded him as their patron: for all he was the personification of the ideals of Christian chivalry. [The Oxford Dictionary of Saints]
worm (n.): Old English wurm, variant of wyrm "serpent, snake, dragon, reptile," also in later Old English "earthworm," from Proto-Germanic *wurmiz (source also of Old Saxon, Old High German, German wurm, Old Frisian and Dutch worm, Old Norse ormr, Gothic waurms "serpent, worm"), from PIE *wrmi- "worm" (source also of Greek rhomos, Latin vermis "worm," Old Russian vermie "insects," Lithuanian varmas "insect, gnat"), probably from root *wer- (3) "turn" (see versus).

The ancient category of these was much more extensive than the modern, scientific, one and included serpents, scorpions, maggots, and the supposed causes of certain diseases. For substitution of -o- for -u-, see come. As an insult meaning "abject, miserable person" it dates from Old English. Worms "any disease arising from the presence of parasitic worms" is from late Old English. Can of worms figurative for "difficult problem" is from 1951, from the literal can of worms a fisherman might bring with him, on the image of something all tangled up.
angel (n.): 14c. fusion of Old English engel (with hard -g-) and Old French angele, both from Latin angelus, from Greek angelos "messenger, envoy, one that announces," possibly related to angaros "mounted courier," both from an unknown Oriental word (Watkins compares Sanskrit ajira- "swift;" Klein suggests Semitic sources). Used in Scriptural translations for Hebrew mal'akh (yehowah) "messenger (of Jehovah)," from base l-'-k "to send." An Old English word for it was aerendgast, literally "errand-spirit."

Of persons, "loving; lovely," by 1590s. The medieval gold coin (a new issue of the noble, first struck 1465 by Edward VI) was so called for the image of archangel Michael slaying the dragon, which was stamped on it. It was the coin given to patients who had been "touched" for the King's Evil. Angel food cake is from 1881; angel dust "phencyclidine" is from 1968.
schmuck (n.): also shmuck, "contemptible person," 1892, from East Yiddish shmok, literally "penis," probably from Old Polish smok "grass snake, dragon," and likely not the same word as German Schmuck "jewelry, adornments," which is related to Low German smuck "supple, tidy, trim, elegant," and to Old Norse smjuga "slip, step through" (see smock).

In Jewish homes, the word was "regarded as so vulgar as to be taboo" [Leo Rosten, "The Joys of Yiddish," 1968] and Lenny Bruce wrote that saying it on stage got him arrested on the West Coast "by a Yiddish undercover agent who had been placed in the club several nights running to determine if my use of Yiddish terms was a cover for profanity." Euphemized as schmoe, which was the source of Al Capp's cartoon strip creature the shmoo.

"[A]dditional associative effects from German schmuck 'jewels, decoration' cannot be excluded (cross-linguistically commonplace slang: cf. Eng. 'family jewels')" [Mark R.V. Southern, "Contagious Couplings: Transmission of Expressives in Yiddish Echo Phrases," 2005]. But the English phrase refers to the testicles and is a play on words, the "family" element being the essential ones. Words for "decoration" seem not to be among the productive sources of European "penis" slang terms.